POS0663 GUT INFLAMMATION ASSOCIATED WITH MORE STRUCTURAL DAMAGE IN THE SPINE IN AXIAL SPONDYLOARTHRITIS. RESULTS FROM THE SPARTAKUS COHORT
Authors: J. K. Wallman, E. Mogard, J. Sagard, K. Andréasson, J. Marsal, M. Geijer, T. Olofsson, E. Lindqvist
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> While 5-10% of axial spondyloarthritis (axSpA) patients have diagnosed inflammatory bowel disease (IBD), 50-60% display microscopic gut inflammation upon examination of mucosal biopsies. Gut inflammation, as measured by faecal calprotectin (F-calprotectin), is more frequent in radiographic (r-axSpA) than non-radiographic axSpA (nr-axSpA) and has been linked to more active disease [1] – a known risk factor for structural damage progression. How gut inflammation relates to the degree of structural damage in the spine, however, remains sparsely studied. <h3>Objectives</h3> To assess if gut inflammation, as measured by elevated F-calprotectin, is associated with more structural damage in the spine in patients with axSpA. <h3>Methods</h3> Patients with clinical axSpA from a defined area of southern Sweden were cross-sectionally examined and classified as nr-axSpA (ASAS criteria; n=85) or r-axSpA (modified NY or ASAS criteria; n=171). Twenty-four (9.4%) subjects had comorbid IBD. Spinal structural damage was quantified by the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS; one experienced reader scored all examinations), and gut inflammation by F-calprotectin (Calpro AS ELISA). mSASSS scores of patients with normal F-calprotectin (&lt;50 mg/kg) were compared to those with elevated (≥50 mg/kg) or substantially elevated (≥150 mg/kg) values, respectively (Mann Whitney U-test). Furthermore, to explore if presence of gut inflammation (F-calprotectin ≥50 mg/kg) was associated with an mSASSS score above the median, logistic regression analysis was used, adjusting for sex, symptom duration, HLA-B27-status, smoking (ever/never), CRP, NSAID (ASAS 3-month NSAID-score) and anti-TNF therapy (yes/no) use. Apart from assessing the overall axSpA group, analyses were also performed limited to subjects with r-axSpA, since both mSASSS and F-calprotectin values were expected to be higher in r-axSpA. Finally, analyses were also repeated after exclusion of patients with IBD as a sensitivity analysis. <h3>Results</h3> Characteristics of the included patients are displayed in the <b>Table 1</b>. In the overall axSpA group, mSASSS scores were significantly higher among patients with elevated F-calprotectin, and even more so among those with substantially elevated F-calprotectin, as compared to subjects with normal values (<b>Figure 1</b>). Similar results were seen when limiting the assessment to r-axSpA, although here mSASSS was significantly higher only among those with substantially elevated F-calprotectin (<b>Figure 1</b>). F-calprotectin ≥50 mg/kg was associated with having an mSASSS score above the median (&gt;2 in the overall axSpA and &gt;5 in the r-axSpA groups, respectively) in both study populations – all axSpA: adjusted odds ratio (OR) 2.2 (95%CI 1.1-4.3), p=0.019; r-axSpA: adjusted OR 2.7 (1.1-6.7), p=0.028. Excluding patients with comorbid IBD rendered similar results. <h3>Conclusion</h3> Presence of gut inflammation, as measured by elevated F-calprotectin, is associated with more structural damage in the spine in patients with established axSpA, as well as specifically in r-axSpA, even after adjustment for known risk factors of spinal damage development. This calls for prospective studies, assessing gut inflammation as a potential predictor of radiographic progression. <h3>Reference</h3> [1]Olofsson T, et al. <i>Rheumatology (Oxford</i>). <b>2019</b>;58:1176-87. <h3>Acknowledgements</h3> Tor Olofsson and Elisabet Lindqvist contributed equally. <h3>Disclosure of Interests</h3> Johan K Wallman Speakers bureau: AbbVie, Amgen, Grant/research support from: AbbVie, Amgen, Eli Lilly, Novartis, Pfizer, Elisabeth Mogard Speakers bureau: AbbVie, Novartis, Jonas Sagard: None declared, Kristofer Andréasson: None declared, Jan Marsal Speakers bureau: AbbVie, Amgen, Bayer, Biogen, BMS, Ferring, Galapagos, ITH, Janssen, Lument, MSD, Otsuka, Pfizer, Sandoz, Takeda, Tillotts, UCB, Grant/research support from: AbbVie, BMS, Calpro AS, Carbiotix, Ferring, Fresenius Kabi, Pfizer, Svar Life Science, Takeda, Mats Geijer Speakers bureau: AbbVie, UCB, Tor Olofsson Consultant of: Eli Lilly, MSD, Elisabet Lindqvist: None declared.